1. Field of the Invention
The present invention relates to a semiconductor device including a semiconductor chip embedded or packaged in a resin package having resin bumps protruding therefrom to form external connection terminals provided with a metal film thereon.
2. Description of the Related Art
FIG. 1 is a cross-sectional view of a conventional semiconductor device including a semiconductor chip 10 embedded or packaged in a resin package 12 having resin bumps 16 protruding therefrom to form external connection terminals 14 provided with a metal film 18 formed thereon by plating. A bonding wire 20 electrically connects an electrode terminal of the semiconductor chip 10 and the metal film 18 for external electrical connection. A resin cover 22 protects the back side of the semiconductor chip 10 by preventing the chip 10 from being exposed to the air.
FIG. 2 is a bottom view of the semiconductor device of FIG. 1 and shows the external connection terminals 14 surrounding the semiconductor chip 10.
The shown structure is advantageous because the electrode terminal of the semiconductor chip 10 is directly connected to the metal film 18 of the external connection terminal 14 through the bonding wire 20 and requires no space for further wiring between the external connection terminal and the bonding wire, which facilitates miniaturization of semiconductor devices.
FIGS. 3(a) to 3(e) are cross-sectional views showing the process of producing the semiconductor device shown in FIGS. 1 and 2.
Referring to FIG. 3(a), a photoresist is applied onto a metal base 30 such as a copper foil, followed by exposure to light and development to form a resist pattern 32 having windows or openings at positions for forming external connection terminals 14 (FIG. 1).
In the next step shown in FIG. 3(b), the metal base 30 is etched using the resist pattern 32 as an etching mask to form recesses 34 in the metal base 30.
As shown in FIG. 3(c), the metal base 30 is subject to plating to form a metal film 18 on the bottom and side wall of the recesses 34 to provide a conductor cap of an external connection terminal to be connected to a semiconductor chip by wire bonding.
In FIG. 3(d), a semiconductor chip 10 is bonded to, and mounted on, the metal base 30 in a predetermined position with a protective resin 22 and electrode terminals of the semiconductor chip 10 are wire-bonded to the metal films 18 within the recesses 34.
In FIG. 3(e), resin packaging is then carried out so that the semiconductor chip 10, the bonding wire and the metal film 18 are embedded in a resin package 12. The portion of the resin filling the recess 34 forms a resin bump having a height of about 0.3 mm, for example. The recess 34 has a depth corresponding to the height of the resin bump.
The metal base 30 is finally removed by solving or etching to complete the semiconductor device shown in FIG. 1. The metal film 18 must be composed of a metal or metal alloy which is not solved during etching of the metal base to provide an external connection terminal composed of a resin bump having a conductor cap 18 protruding from the rear surface of the resin package 12.
Instead of removal by solving or etching, the metal base 30 can be otherwise removed by exfoliating the base metal 30 from the resin package 10 to complete the semiconductor device shown in FIG. 1.
As can be seen from FIGS. 3(c) and 3(d), the conductor cap or metal film 18 has an open end (or an upper end) which protrudes from the metal base 30 at a height of the thickness of the resist pattern 32 and enters a short length the resin package 12 to provide holding of the metal film 18 by the resin package 12 in addition to adhesion of the metal film 18 to the resin bump 16 (FIG. 1).
However, the conventional semiconductor device has a problem because the metal film 18 is occasionally exfoliated from the resin bump 16 when adhesion therebetween is weak.
The object of the present invention is to provide a semiconductor device including a semiconductor chip embedded or packaged in a resin package having resin bumps protruding therefrom to form external connection terminals provided with a metal film formed thereon, in which the metal film is prevented from undesirably exfoliated from the resin bumps thereby providing improved reliability of the semiconductor device.
To achieve the object according to the first aspect of the present invention, there is provided a semiconductor device which comprises a semiconductor chip packaged in a resin package and having an electrode terminal wire-bonded to a conductor cap having one end defining an exposed top of an external connection terminal protruding from the resin package and the other end defining an orifice embedded in the resin package, wherein:
the orifice of the conductor cap has a radially outward extending flange which anchors the conductor cap to the resin package.
According to the second aspect of the present invention, there is also provided a process of producing a semiconductor device, the process comprising the steps of:
forming in one side of a metal base a recess having a stepped orifice with a diameter greater than that of the other portion of the recess;
forming a metal film covering an inner surface of the recess including the stepped orifice so that the metal film forms a conductor cap having an orifice provided with a radially outward extending flange defined by the stepped orifice of the recess;
etching the metal base to partially expose the conductor cap from the metal base so that the flange of the conductor cap is apart from the metal base with a gap therebetween while the conductor cap in a portion other than the flange remains embedded in the metal base;
mounting a semiconductor chip on the metal base with a resin layer intervening therebetween;
wire-bonding an electrode terminal of the semiconductor chip to an inner surface of the conductor cap with a bonding wire;
packaging the semiconductor chip, the bonding wire and the conductor cap with a packaging resin so that the packaging resin fills the conductor cap to form a resin bump and fills the gap between the flange of the conductor cap and the metal base to cause the flange to anchor the conductor cap to the packaging resin; and
removing the metal base by solving to form an external connection terminal protruding from the packaging resin, the external connection terminal being composed of the resin bump having a top covered with the conductor cap having the flange embedded in the packaging resin.
According to the third aspect of the present invention, there is further provided a process of producing a semiconductor device, the process comprising the steps of:
forming a recess in one side of a metal base;
forming a plating mask on said one side of the metal base, the plating mask having a window through which the recess is exposed and which has a diameter greater than that of the recess so that the window defines a surrounding area of a surface of the metal base that either entirely or partially surrounds an open end of the recess;
forming a metal film covering an inner surface of the recess and the surrounding area so that the metal film forms a conductor cap having a radially outward extending flange defined by the surrounding area;
etching the metal base to partially expose the conductor cap from the metal base so that the flange of the conductor cap is apart from the metal base with a gap therebetween while the conductor cap in a portion other than the flange is embedded in the metal base;
mounting a semiconductor chip on the metal base with a resin layer intervening therebetween;
wire-bonding an electrode terminal of the semiconductor chip to an inner surface of the conductor cap with a bonding wire;
packaging the semiconductor chip, the bonding wire and the conductor cap with a packaging resin so that the packaging resin fills the conductor cap to form a resin bump and fills the gap between the flange of the conductor cap and the metal base to cause the flange to anchor the conductor cap to the packaging resin; and
removing the metal base by solving to form an external connection terminal protruding from the packaging resin, the external connection terminal being composed of the resin bump having a top covered with the conductor cap having the flange embedded in the packaging resin.